Method of removing manganese containing deposits



United States Patent 3,526,545 METHOD OF REMOVING MANGANESE CONTAINING DEPOSITS Richard G. Abowd, Jr., Farmington, Mich, assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed July 24, 1967, Ser. No. 655,284

Int. Cl. C23g 1/02 US. Cl. 134-3 Claims ABSTRACT OF THE DISCLOSURE of carbon, hydrogen and oxygen. Oxalic acid is a useful acid.

BACKGROUND OF THE INVENTION Smoke produced during the operation of a distillate fuel burning engine, such as a jet engine, is undesirable. It contributes to air pollution. It indicates reduced engine efliciency.

This exhaust smoke may be reduced by adding suitable additives to the fuel. Especially effective additives are certain cyclopentadienyl manganese tricarbonyls, such as (methylcyclopentadienyl)manganese tricarbonyl. US. 2,818,417 provides a thorough list of useful compounds of this type, and includes methods of preparing them. Although use of these manganese additives substantially reduces the exhaust smoke, a secondary problem may arise in some instances. On combustion of the fuel containing the manganese compound, manganese containing deposits are formed on the engine surface which are contacted by the exhaust products. As with many engine deposits, an effective method of removing these manganese containing deposits is desirable.

SUMMARY OF THE INVENTION A method of removing manganese containing deposits formed on the surfaces of jet engines which burn fuels containing organo manganese compounds, which comprises treating the deposit coated surfaces with an aqueous solution of a mono or dicarboxylic acid composed solely of carbon, hydrogen and oxygen and having up to 10 carbon atoms.

Thus, manganese containing deposits formed in jet engines can be removed by treating the deposit coated surfaces with an aqueous solution of an acid such as oxalic acid. This provides a simple and effective method for cleaning the engine; it is especially advantageous because the engine can be cleaned without disassembling it.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of this invention is a method of removing manganese containing deposits formed on the surfaces of a jet engine from burning a fuel containing a smoke reducing quantity of a cyclopentadienyl manganese tricarbonyl having up to 17 carbon atoms, which comprises treating said surfaces with an aqueous solution of an organic acid composed solely of carbon, hydrogen and oxygen and having up to 10 carbon atoms.

Another embodiment of said method is treating the manganese containing deposit coated surface with a 0.1 to about 50 percent by weight aqueous solution of a C C dicarboxylic acid.

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In a more preferred embodiment, the acid is oxalic acid; a most preferred embodiment utilizes a 5-10 percent by weight oxalic acid solution.

Manganese compounds which are useful as smoke reducers in jet fuels are cyclopentadienyl manganese tricarbonyls having the formula wherein R is a cyclopentadienyl hydrocarbon radical having from 5 to 17 carbon atoms. US. 2,818,417, issued Dec. 31, 1957, contains an extensive disclosure of the type of manganese compounds which are useful. This listing of compounds is incorporated by reference.

(Methylcyclopentadienyl)manganese tricarbonyl is an especially effective smoke reducer.

The concentration of the manganese tricarbonyl in the jet fuel may be varied. Concentrations from 0.025 to about 6.45 grams of manganese per gallon as a cyclopentadienyl manganese tricarbonyl are useful.

By jet fuels, we include distillate hydrocarbons and blends which are useful as fuel for jet engines. These fuels are principally hydrocarbon distillates heavier than gasoline. In other words they are distillate hydrocarbon fuels having a higher end point than gasoline. They are generally composed of distillate fuels and naphthas and blends of the above, including blends with lighter hydrocarbon fractions. The end point of preferable jet fuels is at least 435 F. and more preferably greater than 470 F.

Typical jet fuels include JP3, a mixture of about percent gasoline and 30 percent light distillate having a percent evaporation point of 470 F JP-4, a mixture of about 65 percent gasoline and 35 percent light distillate especially designed for high altitude performance; JP-S, an especially fractionated kerosene and the like.

The manganese containing deposit which is formed on the jet engine surfaces comprises a mixture of compounds. Principal components of this mixture are the oxides such as Mn O and Mn O Organic acids which are useful in the method of this invention are mono and dicarboxylic acids composed solely of carbon, hydrogen and oxygen and having up to 10 carbon atoms. Examples of useful acids are formic acid, Z-ethyl hexanoic acid, pentanoic acid, decanoic acid and the like. Preferred acids are dicarboxylic acids. Examples of preferred acids are sebacic acid, suberic acid, adipic acid, malonic acid and the like.

Oxalic acid is an especially preferred acid.

An outstanding feature of the present invention is that it offers a method of removing manganese containing deposits in a jet engine without requiring its disassembly or its removal from its mounting. Thus, the engine can be cleaned while it is still in place in an airplane fuselage for example, by simply spraying the organic acid solution described above, through the engine, while the engine is being cranked. Cranking a jet engine means that the engine is turning :but the fuel is not ignited. By cranking the engine, all the engine surfaces which may have a manganese containing deposit become exposed to the spray.

Another method of spraying the solution into the jet engine is to feed it through the fuel feed system between the fuel tank and the combustion area. Using this procedure, the solution will contact only those engine surfaces on which the fuel and exhaust products would impinge. The engine is cranked to insure better contact. In

"either case, the spray may be continuously recycled if 3 an immersion or after a spray treatment, the engine is generally rinsed with a pure water. A combination of the spray soak procedure can also be used.

The engine treatment can be carried out either before or after the engine has cooled after being in operation. The solution with which the treatment is carried out may also be warmed, if desired. By treating the engine while hot or by using a hot solution, treatment time to clean the engine can be reduced. Heating either the engine surfaces or the solution, however, is not required. Whatever means is used to carry out the engine treatment, the only requirement is that a solution, as herein described, contact the manganese containing deposits on the engine surfaces.

The effectiveness of the aqueous acid treatment was determined in a laboratory procedure using a metal test specimen on which was deposited at manganese containing deposit. The test specimen was prepared by allowing the exhaust stream from burning a jet fuel containing about 0.1 volume percent (1.29 g./ gal. of manganese) of (methylcyclopentadienyl)manganese tricarbonyl, to impinge on the metal piece. The manganese containing deposit appeared as a brownish tan deposit on the metal surface. This test specimen was then immersed in a vessel containing about 200 parts of the aqueous acid solution to be tested. The solution was then warmed in a steam bath to above about 70 C. The effect of the solution on the deposit was observed. The effective aqueous acid solutions dissolved a substantial portion of the tan manganese containing deposit, leaving the metal piece practically free of the deposit. This dissolution began almost immediately on placing the specimen in the test solution and was considered to be practically complete after about minutes of warming on the hot plate.

Using this test procedure, five per cent oxalic acid solution was found to dissolve the manganese containing deposit very readily. A five percent malonic acid solution was also found to be effective.

Similar results are obtained using a 0.1 percent adipic acid solution; a 50 percent acetic acid solution; a two percent suberic acid solution; a 10 percent propionic acid solution; a three percent sebacic acid solution or a percent formic acid solution, in the test procedure described above.

Another procedure used to evaluate the effectiveness of the acid solutions in removing the manganese containing deposits comprised a spray-soak procedure. In this procedure, the test specimens, prepared as described above were weighed. They were then mounted on a rotary spindle enclosed in a sheet metal shroud. The spindle was rotated and the acid solution was sprayed on the rotating parts for five minutes. The spindle was then stopped and allowed to set for five minutes. This cycle was repeated three times. At the end of this thirty minute cycle the spindles were dried and reweighed. The results were expressed as percent deposit dissolved. The following data was obtained using this soak-spray procedure. A water spray alone removed no deposits.

Manganese containing Test solution deposit dissolved 10 1 percent oxalic acid 60 percent 10 1 percent oxalic acid 61 percent 1 By weight.

The data presented above clearly demonstrates that the manganese containing deposits formed on jet engine parts can be effectively removed by treatment with an aqueous organic acid solution as herein described. The manganese containing deposit has been described as that being formed from burning jet fuel containing a cyclopentadienyl manganese tricarbonyl. However, it is considered within the scope of the present invention that the present method will be effective for removing manganese containing deposits obtained on burning jet fuel containing other manganese bearing additives.

The process of the present invention is described above. It is intended that the present invention be limited only within the lawful scope and extent of the following claims.

I claim:

1. A method of removing manganese containing deposits formed on the surfaces of a jet engine from burning a fuel containing a smoke reducing quantity of a cyclopentadienyl manganese tricarbonyl wherein the cyclopentadienyl radical has up to 17 carbon atoms, which comprises treating said surfaces with an aqueous solution consisting of a dicarboxylic acid composed solely of carbon, hydrogen and oxygen and having from 2 to about 10 carbon atoms, and water.

2. The method of claim 1 wherein said cyclopentadienyl manganese tricarbonyl is (methylcyclopentadienyl) manganese tricarbonyl.

3. The method of claim 1 wherein the concentration of said acid in aqueous solution is from 0.1 to about 50 percent by weight.

4. The method of claim 3 wherein said acid is oxalic acid.

5. The method of claim 4 wherein the concentration of said acid solution is from about 5 to about 10 percent by weight.

6. The method of claim 3 wherein said fuel contains from 0.025 to about 6.45 grams of manganese per gallon as said cyclopentadienyl manganese tricarbonyl.

7. The method of claim 6 wherein said cyclopentadienyl manganese tricarbonyl is (methylcyclopentadienyl) manganese tricarbonyl.

8. The method of claim 7 wherein said acid is oxalic acid.

9. The method of claim 8 wherein said fuel contains about 0.1 volume percent of said (methylcyclopentadienyl)manganese tricarbonyl.

10. The method of claim 9 wherein the concentration of said oxalic acid in aqueous solution is from about 5 percent to about 10 percent by Weight.

References Cited UNITED STATES PATENTS 2,992,995 7/1961 Arden 13420 XR 3,025,189 3/1962 Arden 1343 3,216,857 11/1965 Duvall 134-3 MORRIS O. WOLK, Primary Examiner J. T. ZATARGA, Assistant Examiner US. Cl. X.R. 134-22, 39 

